Numerous optical brightener materials are used in detergent compositions. Such materials are designed to deposit onto fibers and fabrics and to alter the chromaticity of items to yield a more preferred white. Optical brighteners work by converting invisible, ultraviolet radiation to a visible blue frequency which shifts the chromaticity of a surface away from a yellow cast to a preferred clean bluish cast.
In general, such optical brightener molecules have at least one relatively large chromophoric group and one or more substituent groups. For use in laundry detergents, the molecules must not only exhibit the correct optical properties, but also must be capable of being deposited onto fabrics from an aqueous wash liquor containing various surfactants, detergency builders and other detersive adjuncts.
Detergent compositions containing optical brighteners may be formulated in a number of ways. One formulation method involves adding the brightener to the detergent composition as a free powder. However, this preparation method causes problems such as dusting, which can be particularly troublesome at a detergent composition manufacturing site. Another problem with this formulation method is that optical brighteners can require long dispersing times when added as powders to liquid detergent compositions.
One method of avoiding such dusting and dispersion problems is to add the brighteners to the liquid detergent compositions via a premix which contains the optical brighteners and an additional compound.
However, other problems arise when optical brighteners are added to liquid detergent compositions as a premix, especially when added to highly built liquid detergent compositions. For example, when the optical brightener is combined with nonionic surfactants such as Neodol.RTM. in the premix, the addition of the premix to highly built liquid detergent compositions causes haziness and phase separation. When the optical brightener is combined with alkyl polyglycoside in the premix, the addition of the premix to highly built liquid detergent compositions results in a milky, one-phase product.
Therefore, it would be desirable to develop a premix by which brighteners can be added to highly built liquid detergent compositions which avoid such problems. It has now been discovered that if brighteners are added to such detergent compositions via a premix containing the brighteners and certain polyhydroxy fatty acid amides, the aforementioned dusting and dispersing problems can be avoided. Furthermore, adding brighteners via such a premix allows for the formulation of clear, isotropic, highly built liquid detergent compositions. Additionally, the use of such a premix, in certain cases, allows for formulation and performance flexibility by enabling facile addition of optical brighteners which are otherwise difficult to incorporate into liquid detergent compositions.